Brasilia Captain - You saved me reading the relevant FCOM pages again!
An advantage of the prop brake is that one doesn't have to ask for ATC start clearance to start No.2 in Hotel mode, since the prop isn't turning. Also, in my outfit at least, we will typically start No.2 in Hotel mode, then disconnect the GPU, then start No.1, release the prop brake, and put both props to MAX RPM prior to taxi (alternatively, we can start both before disconnecting the GPU). Probably saves a bit of time on handling procedures.
NAC OVHT is indeed an issue in a tailwind; you're there minding your own business, when suddenly you get an MW, a CRC and NAC OVHT on the CAP. You can then either:
1/ Release the prop brake to create airflow over the nacelle - not really feasible when waiting for a GPU (but OK if it happens while you're taxying)
2/ Shut down No.2 - but then you're on battery only (unless you want that OFF too)
As with every system, it's OK as long as you know its limitations.
Cheers
